1. Field of the Invention
The present invention relates to a method for constructing a surface that is used to increase the degree of freedom of the expression or the like of a surface shape in an expression of a fluid-body simulation implemented by a particle-based calculation, to a program for the method, and to a storage medium for storing the program.
2. Description of the Related Art
A “particle-based simulation” is a simulation method for performing calculations relating to the behavior of each of a large number of particles, in which the object of the simulation is a group (aggregation) of numerous particles. “Spheres” having a constant diameter are usually used as the particles for calculation by computer. When the shape of the object is expressed by an aggregation of spheres, the degree of approximation or the spatial resolution varies depending on the method of determining the size (diameter) of the spheres. Varying the sphere diameter and varying the spatial resolution make it possible to control the calculation accuracy and the calculation speed in the computer simulation calculation.
The abovementioned particle-based simulation has been used in recent years to calculate collisions of numerous rigid bodies, and to calculate the behavior of fluids, particulate bodies, and the like, and to research simulations of collisions, flow, and the like on the screen of a computer display device. The results of this research are described in M. Tanaka et al., “Development of a rigid-body calculation method using a particle method, and application thereof to computer graphics,” Japan Society of Mechanical Engineers, Papers of the 19th Computational Mechanics Conference, pp. 701-702, 2006, for example. Research of these simulation techniques is important for the technology that forms the foundation of computer graphics (CG).
In the calculation of a particle-based fluid-body simulation, since the particles as such express a fluid body, there is no need to perform interface tracking, and the flow of a free surface can easily be calculated. In the calculation of the surface of a fluid body, when the calculation results based on a particle method are rendered and displayed on a display screen, concentration spheres are allocated to a plurality of spheres obtained by calculation, and a curved surface of an implicit function is constructed to compute the surface of the fluid body. An example of this calculation is described in J. Blinn, “A generation of algebraic surface drawing,” ACM Transactions on Graphics, 1 (3): 235-256, 1982, or in M, Muller, D. Charypar, and M. Gross, “Particle-based fluid simulation for interactive applications,” In proc. Of SIGGRAPH Symposium on Computer Animation, pp. 154-159, 2003, for example. However, when the surface is calculated by such a calculation, it is difficult to express thin films or sharp edges that occur in the change state of the fluid body.
There has been a need for the ability to compute and display an expression of thin films or sharp edges in fluid body in the display of a particle-based fluid-body simulation.